Tamerlan Tsarnaev died in a shootout, and his younger brother was captured alive. They were identified by authorities and relatives as ethnic Chechens from southern Russia who had been in the U.S. for about a decade.

According to FBI, the foreign government said that based on its information, Tamerlan Tsarnaev was a strong believer and that he had changed drastically since 2010 as he prepared to leave the U.S. for travel to the country's region to join unspecified underground groups.

The FBI says it interviewed Tsarnaev and relatives, and did not find any domestic or foreign terrorism activity.

Photo timeline: Boston Marathon bombing

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This photo taken before the bombings shows suspect Dzhokhan Tsarnaev in the background with what may be the bomb in a backpack in the lower part of the frame near the railing.